点缺陷对B2-NiAl力学与热学性能影响的第一性原理计算

基于密度泛函理论的第一性原理平面波赝势法，计算了反位缺陷与空位对B2-NiAl力学与热学性能的影响．采用杨氏模量、剪切模量、弹性常数、Cahchy压力、泊松比、Debye温度、比热、热膨胀系数等参数评判反位缺陷与空位对B2-NiAl合金的延性、硬度及热学性能的影响．结果表明：NiAl,VNi均能提高B2-NiAl晶体的硬度而降低其本征延性，AlNi与vAl对晶体力学性能的影响可以忽略不计．点缺陷对晶体比热的影响均集中在Debye温度以下，在此温度范围内，4种点缺陷均能降低晶体的比热，降幅从高到低依次为VNi〉NiAl〉A1Ni〉VAl．而当温度高于1000K时，4种点缺陷对晶体比热的影响基本消失而使比热趋于同一数值25J／mol·K．当温度高于600K时，对晶体相对热膨胀系数影响较明显的点缺陷是vAl，与NiM前者使晶体的相对热膨胀系数提高，而后者使晶体的相对热膨胀系数降低．

First-principles calculation on mechanical and thermal properties of B2-NiAl with point defects

Using the first-principles pseudopotential plane-wave methods based on the density functional theory, the effects of antisite defect and vacancy on the mechanical and thermal properties of B2-NiAl intermetallics compound were discussed. Several parameters, such as Youngs modulus, the shear modulus, the elastic constant, Cauchy pressure, Poisson ratio, Debye temperature, specific heat and the thermal expansion coefficient, have been calculated to judge effects of the antisite defect and vacancy on the ductility, hardness and thermal properties of B2-NiAl. The results show that the point defets of NiA;, VNi all improve the hardness of B2-NiAl and reduce its ductility, while AlNl, VA; have hardly effects on the mechanical properties of B2-NiAl. Under the Debye temperature, four point defects all reduce the specific heat of B2-NiAl as following order： VNl〉NiAl〉AlNl〉VAl. But when the temperature is above 1000 K, the effects of the four point defects on specific heat of B2-NiAl are vanish and make the value of specific heat tend to a constant 25 J/mol.K. When the temperature is above 600 K, VAl and NiAl can prominently change the relative thermal expansion coefficient of B2-NiAl, the former can improve the value of the relative thermal expansion coefficient and the latter can reduce its value.